Diaphragm for telephone receivers



Jan. 19 1926. 1.570,33?

" P. J. COOK DIAPHRAGMFOR TELEPHONE RECEIVERS Filed MaICh 25, 1925- INVENTOR Da/mer J (Y0U/f ATTORNE.

Patented dan. 1Q, 192@ FARMER il'. COOK, OE SOUTHFEELD, MASSACETJSETTS.

IDEAPHRGM FOR TELEPENE RECEUIES.

Application tiled March 23, 1925. Serial N0. 17,661.

To @ZZ whom t may concern.'

Be it known that l, PALMER d. Coon, a citizen of the United States, and a resident of Southfield, county of Berkshire, and State of Massachusetts, have invented certain new and. useful Improvements in Diaphragms for Telephone Receivers, ci? which the following is a specification.

rihis invention relates to telephone receivers, and more particularly to an improved form of diaphragm for use in a telcphone receiver, a radio headset, a loud speaker, or the like. l

@ne object of this invention is to provide a diaphragm of the above nature which will be constructed partly ot iron and partly of non-metallic material, and which will be used in place of the all-metal diaphragms now on the market.

A further object is to provide a diaphragm of the above nature which will faithfully reproduce the transmitted sound vibrations without distortion `tlnoughout practically the entire range of audible frequencies.

A -further object is to provide a device of this nature which will be simple in construction, inexpensive to manufacture, practical- .ly unbreakable, and very efiicient and durable in use.

'li/Vith these and other objects in view there have been illustrated on the accompanying drawings, two forms in which the invention may be conveniently embodied in practice.

Fig. 1 represents a side view, partly in section, of a radio headset in which the rst form of diaphragm has been installed.

Fig. 2 is a plan view of the diaphragm shown separately.

F ig. 3 is a sectional view of the same.

Figs. 1 and 51 are plan and sectional views respectively of a second and modiiied form of diaphragm, also embodying the invention.

lin the use of telephone receiving instruments, and more particularly those instruments employed for the reception ci' radio 'broadcasted'programs, it has been previously impossible to obtain satisfactory reproduction of the transmitted sounds, and a certain amount of distortion was always encountered. 'llhis has been due largely to the fact that the iron diaphragms necessarily employed would not respond equally well to sounds `ont all different wave lengths. Mereover inthe use ot such all-metal. diaphragms, a metal-lic tone to the sounds produced.

By, means ot' the present invention, the above and other disadvantages have been largely avoided. This has been accomplished by providing a diaphragm consisting ot a material formed by combining a non-metallic material with iron. lt has been discovered that such a diaphragm will reproduce the natural tones of sound waves quite faithfully over the entire range ot' audible frequencies, and at the same time will practically eliminate the metallic tone formerly noticed.

Referring now 'to the drawings in which like reference numeralsdenote corresponding parts throughout the several Views, the iirst embodiment of the invention is illustrated in Figs. 1, 2, and said figures, the diaphragm comprises a circular disc l0 ot tlat sheet material made from rawhide scrap7 or grindings mixed with a suthcient amount of finely divided soft iron to render the material susceptible to the magnetic oscillations in the field surrounding an electromagnet. lt has been found in one example that a material containing an equal part of iron filings, or iron dust, and rawhide produces a satisfactory diaphragm. rThe sheeting of said material is preferably done in a mold under heat and high pressure.

1t has been 'found in practice that a pressure of six to seven tons per square inch is necessary to produce the required degree of strength and solidity in the sheet material.

The diaphragm 10 is made'of such a size that it will seat on the periphery of a threaded casing 12 ot a telephone headset, and said diaphragm 10 is adapted to be held securely in position by means of an annular cover member 13, which is tapped with internal threads and is adapted to screw upon the external threads of said casing 12. The face of the cover member 13 is cupped inwardly and is provided with a central aperture 14 through which the sounds produced by the diaphragm may travel.` ln the operation of the device, it will be understood that the combination rawhide and iron diaphragm will vibrate-in response to the varying magnetic field of the electromagnet 11, which in turn is responsive to the uctuating current in Wires l5 connected to a radio receiving set or other was also imparted As shown inv instrument receiving impulses from a transmitting'instrument. y

In order 'to render the diaphragm more durable and less sensitive to atmospheric conditions, it may be given a coating 16 of any suitable strong waterproof material such as shellac, varnish, or the like.

In Figs. 4 and 5, the 4second `or modified form of combination metal and non-metal diaphragm is disclosed. This form of diaphragm is identical in shape with the diaphragm 10 illustrated in Figs. 1, 2', and 3,- and comprises a disc 17 made from a sheet of hot-pressed rawhide having embedded in its interior a small circular disc 18 of soft iron. The diameter of the small disc 18 is preferably, though not necessarily, less than one-half the diameter of the diaphra 17 itself. It will 'be understood that 1n this modified form of the invention,

the small iron disc 18 will 'respond to the fluctuating field of the electromagnet 14 and will communicate its motion to the entire diaphragm 17. The modified form of diaphragm 17 is preferably given a coating 19 of strong waterproof material, asin the first form of the invention shown in Figs. 1, 2, and 3.

One advantage of the present invention is that the combination umetal and non-metal diaphragm, serves to bring out music and other sounds with great detail and reproduces equally Well all sounds between the extreme ends of the scale of audible frequencies.

While the invention has been herein illustrated as being applied to a radio headset, it will be understood that it may equally well be employed in ordinary telephone receivers, loud lspeakers,amplifiers, etc., within its general principles and scope.

While there have been disclosed in this specification two forms in which the invention may be embodied, it is'to be understood that these forms are shown for the purpose' Having thus fully described the inven- 'tion, what is claimed as new, and for which it isfdesired to secure Letters Patent, is:

l. A diaphragm for a telephone receiver consisting of. a-sheet of rawhide having combined therewith'a sheet of iron.

2. A diaphragm for a telephone receiver or amplifier unit consisting of a disc of thin.- sheet rawhide in combination with llOll. A A diaphragm for a telephone receiver or amplifier unit consisting of a thin sheet of rawhide in combination with iron, said diaphragmhaving a waterproof coating.

In testimony whereof, I have alixed my signature to this specication PALMER J. COOK. 

